The invention relates generally to transducers and more specifically concerns a broadband capacitive electrostatic acoustic transducer for ultrasonic measurements in liquids.
Capacitive transducers have been used in the past for ultrasonic measurements in solids (Gauster and Breazeale, The Review of Scientific Instruments, Volume 11, pages 1554-1548, 1966; Cantrell and Breazeale, Journal of the Acoustic Society of America, Volume 61, pages 403-406, 1977). However, neither these nor any other known transducer is suitable for making absolute amplitude ultrasonic measurements in a liquid environment.
It is therefore an object of this invention to provide a capacitive transducer suitable for making absolute amplitude ultrasonic measurements in a liquid environment.
To effectively use a capacitive transducer to make ultrasonic measurements the transducer must be very sensitive. To achieve this high sensitivity it is necessary that the gap between the capacitor plates be extremely small and that the two capacitor plates be as parallel as possible.
Another object of this invention is to provide a method and apparatus for making the two plates of a capacitive transducer parallel and a fixed small distance from each other with a high degree of exactness.
A further object of this invention is to provide a means for applying tension to a membrane capacitive plate to aid in making the two capacitive plates of a capacitive transducer flat and parallel.
Other objects and advantages of this invention will become apparent hereinafter and in the drawings.